Celebrity Guess Who -- Masked Edition!

Heath Ledger! Heath Ledger! Heath Ledger!

Heath Ledger, 28, was spotted Saturday on the set of his new movie The Imaginarium of Doctor Parnassus, which is currently filming in London.

The film, due for release in 2009, also stars Christopher Plummer and is described as a “fantastical morality tale set in the present day”. Here’s the premise of the story: “The leader of a traveling theater troupe who, through a deal with the Devil, takes audience members through a magical mirror to explore their imaginations.”